Round sight glasses Type 321 acc. to DIN 28121 assembly for bolting straight onto DIN flanges

Short description - sight glass fitting DIN28121 for flanges PN10 or PN25

The ACI screw-on tank sight glass Type 321 according to DIN 28121 includes a PTFE-enclosed resilient gasket as inner seal. This gasket is installed in off load contact, with the metal flanges completely surrounding the edge of the glass disc, providing excellent protection.

Type 321 is delivered in assembled condition ready to be mounted onto a carrier flange according to DIN EN 1092-1. In the unlikely case of glass damage during normal operation, Type 321 can be exchanged quickly and without special tools.

The off load gasket pre-empts setting of the fasteners, making a re-tightening of the assembly unnecessary.

The PTFE enclosed gasket makes Type 321 especially suited for use with food, acids, alkaline solutions, and most corrosive chemicals. For the glass disc itself, we offer protective sheets made from mica, PCTFE or FEP to protect the glass surface from most harmful influences.

Accessories like our wipers type SW1, spray nozzles or light fixtures are also available for delivery directly from us.

For the flanges, you can choose from our range of high quality stainless steel, including 1.4541, 1.4404 and 1.4571. or any steel type fitting your specifications. For processes with low corrosion risks, we can also offer low-grade pressure vessel steel alloys like P265GH or S235JRG2. As glass discs, we exclusively use industrially proven MAXOS® borosilicate glass according to the established standard DIN 7080.

Read on for more technical information, detailed 3D views and our product video!

Technical details


Base flange:
1.4404 / 1.4539 /1.4571 / 1.4541 / 2.4602 / 2.4605 / other materials on request

Cover flange:
1.4404 / 1.4539 /1.4571 / 1.4541 / 2.4602 / 2.4605 / other materials on request

Sight glass:
Borosilicatglass DIN 7080


DIN 28121

Nominal size:

DN40 up to DN200

Nominal pressure:

PN10 or PN25 / for higher pressures see type 322


Max. 200 ° C for higher temperatures see type 323


PTFE-enclosed resilient gasket (max. 200°C)

Take advantage of our 360 degree 3D view for a perfect all-round view of our product.

Take a look at the animation video, here you can see the structure of our tank sight glass acc. to. DIN 28121 - type 321 perfectly.

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